Compositions and methods for chemical-mechanical polishing (CMP) the surface of a substrate are well known in the art. Polishing compositions (also known as polishing slurries, CMP slurries, and CMP compositions) for CMP of metal-containing surfaces of semiconductor substrates (e.g., integrated circuits) typically contain an oxidizing agent, various additive compounds, abrasives, and the like.
In conventional CMP techniques, a substrate carrier or polishing head is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the substrate, pressing the substrate against the polishing pad. The pad is moved relative to the substrate by an external driving force. The relative movement of the pad and substrate serves to abrade the surface of the substrate to remove a portion of the material from the substrate surface, thereby polishing the substrate. The polishing of the substrate by the relative-movement of the pad and the substrate typically is further aided by the chemical activity of the polishing composition (e.g., by oxidizing agents present in the CMP composition) and/or the mechanical activity of an abrasive suspended in the polishing composition.
A surface of a substrate is abraded to polish the surface by contacting the surface with a polishing pad and moving the polishing pad relative to the surface, while maintaining a CMP slurry between the pad and the surface. Typical abrasive materials include silicon dioxide, cerium oxide, aluminum oxide, zirconium oxide, and tin oxide.
U.S. Pat. No. 5,527,423 to Neville, et al., for example, describes a method for chemically-mechanically polishing a metal layer by contacting the surface of the metal layer with a polishing slurry comprising high purity fine metal oxide particles suspended in an aqueous medium. Alternatively, the abrasive material may be incorporated into the polishing pad. U.S. Pat. No. 5,489,233 to Cook et al. discloses the use of polishing pads having a surface texture or pattern, and U.S. Pat. No. 5,958,794 to Bruxvoort et al. discloses a fixed abrasive polishing pad.
Many integrated circuits utilize metals for electrical connections between various portions of the circuit. Integrated circuit interconnects typically consist of three-dimensional metal lines with submicrometer cross sections, which are surrounded by insulating material. Commonly, the metals chosen for use as circuit interconnections include aluminum and copper for horizontal interconnects, and tungsten and copper for vertical (interlayer) connections. Tantalum and various tantalum compounds (e.g., tantalum nitride) are frequently utilized as barrier layers to prevent migration of copper into underlying silicon, as well. An integrated circuit interconnect might consist of several one-micrometer-thick layers. CMP compositions for polishing metal-containing surfaces generally include variety of other components to aid in removal of excess metals, barrier layers, polysilicon, and the like, such as oxidizing agents, abrasives, and amino-type corrosion inhibitors, such as benzotriazole, and the like.
The pot-life of conventional polishing compositions containing an amine compound (e.g., benzotriazole) and a radical-forming oxidizing agent (e.g., hydrogen peroxide) typically is not entirely satisfactory, since amines are frequently oxidized by radical-forming oxidizing agents. The oxidation of the amines typically reduces the efficiency of the amines to accomplish their intended purpose (e.g., corrosion inhibition).
Accordingly, there is an ongoing need to develop new CMP compositions that contain amines and radical-forming oxidizing agents, and which have improved pot-life compared to conventional CMP compositions. The present invention provides such improved CMP compositions. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.